Regenerative overvoltage trip during constant speed...

[sw_ross]

I'm working with a Mitsubishi Inverter FR-D700.
The situation is a seasonal usage situation, only being used during the summer months. The VFD worked great all last summer.
In the fall it was removed from its outdoor location and put into storage in a room temperature location so it wasn't in the cold.
I re-installed it a couple of weeks ago. All the previous parameters settings were saved and everything seemed to work fine.
Now they are having issues with the motor stalling out during usage.

VFD is giving the fault code for "Regenerative Overvoltage Trip During Constant Speed".

A parameter setting, "Stall Preventative Operation Level" controls a setting for this, adjustable from 0-200%.
The VFD has the factory default setting at 150%.

I'm not very knowledgeable about VFD's.
I'd like to think about adjusting this setting but just not sure.
I'm not aware of anything that has changed in the setup and usage of the motor from last summer to this summer. It sounds like the load has remained constant from last summer to this summer.

I'm looking for input if anyone has knowledge about this situation.
What are the results of adjusting this parameter either up or down...?

Thanks

 

[ptonsparky]

Has the POCO, or anyone else added PFC? Monitor the incoming voltage at the drive. Do you have a line reactor installed?
Check

 

[Jraef]

Aside from the PFC (or utility line) capacitor possibility, the most common cause if this is a change in the load profile, often something very subtle that you may not have noticed. Can you describe the machine it is used in? For example if it is a blower, if there is a Venturi effect taking place where an external wind across an outlet is pulling air out of a duct faster than the fan wants to push it via the VFD driven motor, the motor becomes a generator and charges the DC bus. The same can happen if it’s a pump that ends up siphoning because the outlet is a hose and someone put the hose lower than it was last year.

 

[sw_ross]

Interestingly, this motor is used in a performance Ampitheater. On the stage they have rails on which 3 different prop buildings are moved back and forth during the performance.

this is a 1 hp motor (208v) 3-phase motor that is used to move a Gazebo forward and back depending on the performance. The music band with instruments is on the gazebo. When the band is going to play music the gazebo is advanced and then reversed when they are done.

I'm wondering whether something related to the load changed. Maybe they added stuff to the gazebo that changed the weight. Maybe the band members gained a bunch of weight over the winter!
Maybe I'll check current draw on motor.

There are error codes for overvoltage during acceleration, overvoltage during deceleration, and overvoltage during constant speed (which is the code being shown). These are related to "regenerative voltage".

I don't know anything related to poco PFC for this facility, or any line reactor.

 

[Fulthrotl]

Interestingly, this motor is used in a performance Ampitheater. On the stage they have rails on which 3 different prop buildings are moved back and forth during the performance.

this is a 1 hp motor (208v) 3-phase motor that is used to move a Gazebo forward and back depending on the performance. The music band with instruments is on the gazebo. When the band is going to play music the gazebo is advanced and then reversed when they are done.

I'm wondering whether something related to the load changed. Maybe they added stuff to the gazebo that changed the weight. Maybe the band members gained a bunch of weight over the winter!
Maybe I'll check current draw on motor.

There are error codes for overvoltage during acceleration, overvoltage during deceleration, and overvoltage during constant speed (which is the code being shown). These are related to "regenerative voltage".

I don't know anything related to poco PFC for this facility, or any line reactor.

i'm not a wizard on VFD's so i'd look at a physical aspect of the installation that is causing
the load to surge against the motor, triggering the code. is something binding? i don't know
how long the overvoltage would have to last to set the code... it it an instantaneous thing?
if something was binding and releasing during function.....

failing that, i'd look and see if there were any electric guitar cords in the instruments on the
gazebo that were wound too tightly. that would do it for sure.

 

[Cow]

Interestingly, this motor is used in a performance Ampitheater. On the stage they have rails on which 3 different prop buildings are moved back and forth during the performance.

this is a 1 hp motor (208v) 3-phase motor that is used to move a Gazebo forward and back depending on the performance. The music band with instruments is on the gazebo. When the band is going to play music the gazebo is advanced and then reversed when they are done.

I'm wondering whether something related to the load changed. Maybe they added stuff to the gazebo that changed the weight. Maybe the band members gained a bunch of weight over the winter!
Maybe I'll check current draw on motor.

There are error codes for overvoltage during acceleration, overvoltage during deceleration, and overvoltage during constant speed (which is the code being shown). These are related to "regenerative voltage".

I don't know anything related to poco PFC for this facility, or any line reactor.

Is there anything that can overspeed the motor beyond the speed the VFD is trying to run it at? For instance, does the track have any slope to it?

 

[paulengr]

What is happening is the VFD is trying to maintain speed but something is pushing/pulling the motor but instead of the usual load trying to slow it down in this case it’s speeding up. The VFD is dumping the excess power back onto the line (regenerative braking) but can’t handle the load. Usually this is more common as an issue when someone tries to decelerate to stop too fast.

The fault should be from something driving the motor so that it is acting like a brake instead of a motor. This is common when decelerating or with hoisting loads or tracks that dip or go down a hill. That’s what you should be looking for. Not as familiar with Mitsubishi but should be a status setting in the drive letting you watch for this or at least current.

 

[sw_ross]

Thanks for all the good replies. All are helpful in giving me an understanding of what might be going on.

As I said before everything worked fine all last summer. Nothing related to the rail system or the mechanics of the setup has changed. The gazebo only moves about 25 feet on the rail system.

When I re-installed it a month ago everything seemed fine during initial testing. They've only experienced the fault during times when the gazebo was under load with all of the band members and instruments. I've been there twice again trying to get it to go into fault mode but couldn't get it to act up...(gazebo was empty)...

What I'm wondering now is that with the gazebo empty of band members while I'm there testing, the load is significantly decreased. Maybe I need to find out how the load has changed from last year to this season.

If something related to a change in load (like an increase) is what's causing the issue I can only imagine the fix would be to increase the HP or change the gearing setup?

 

[Jraef]

Did the position of the band on the stage change, ie the distribution of weight might be further from the center than It was before? That represents more of a “moment of inertia”.

 

[synchro]

Maybe there could be something heavy that swings or rocks (and not just the music ) which could cause some transient regenerative voltage on on the VFD bus.

 

[sw_ross]

Thanks! I'll investigate things further with them tomorrow.
The first thing I want to ask is if they've ever experienced the fault without the band (load) on the gazebo or if it's only when the gazebo is loaded up.

 

[winnie]

If you really have regeneration going on, then you need to do something about the regenerated energy.

If it is transient regen, then a larger inverter might help, simply by virtue of having a larger capacitor bank.

But a braking resistor might be more cost effective.

I don't know these particular inverters. Is it possible that a supply overvoltage could cause this error?

Jon

 

[ptonsparky]

If you really have regeneration going on, then you need to do something about the regenerated energy.

If it is transient regen, then a larger inverter might help, simply by virtue of having a larger capacitor bank.

But a braking resistor might be more cost effective.

I don't know these particular inverters. Is it possible that a supply overvoltage could cause this error?

Jon

Supply overvoltage is one of the items listed in the manual for that fault.
Page 260....”...voltage to reach or exceed the specified value, the protective circuit is activated to stop the inverter output. The circuit may also be activated by a surge voltage produced in the power supply system.”

I think I have the correct manual.

 

[Jraef]

If this is a 400V "class" Mitsi drive, the AC input voltage would have to be >528V to cause an OV trip by itself. Utilities here in the US are supposed to maintain 480V +-5%, so that would be 504V max., meaning for this to come from the utility feed would be WAY outside of acceptable limits if true. Again, capacitors could cause resonance and make the bus THINK there is too much voltage, I've seen that happen. But MOST of the time this sort of thing is load related.

The jamming / binding then releasing is an interesting concept though. Maybe something about the stage warped over the winter months and that warpage is leading to this kind of effect.

If you are not using the output relay or open collector output, you can program them to be a "Regenerative alarm" function to let you know it is about to happen, that may be useful. You can also program the Analog Output to show regenerative energy, then you can watch it or feed that into a recorder.

 

[ptonsparky]

One of the hints from that manual was to make sure the load was stable. I am picturing the entire band in synch with the "Boogie Woogie Boy (of Company B)" as the Gazebo is advanced.

 

[sw_ross]

Since some appear to have looked at the VFD Instruction Manual online (Mitsubishi FR-D700) let me ask this question,

In the troubleshooting section of the manual the error code, E.VO2, is described.
Under "Corrective action" it says to check/set parameter 22 (Stall prevention operation level) and make sure it's "not too small".
This parameter is adjustable from 0-200%. Factory default setting is 150%.
I'm trying to understand what happens if this parameter was adjusted either up or down? And whether it would be useful, or harmful, to adjust this default setting.

 

[ptonsparky]

Since some appear to have looked at the VFD Instruction Manual online (Mitsubishi FR-D700) let me ask this question,

In the troubleshooting section of the manual the error code, E.VO2, is described.
Under "Corrective action" it says to check/set parameter 22 (Stall prevention operation level) and make sure it's "not too small".
This parameter is adjustable from 0-200%. Factory default setting is 150%.
I'm trying to understand what happens if this parameter was adjusted either up or down? And whether it would be useful, or harmful, to adjust this default setting.

Adjust it. That may be all it takes but something changed. You won’t know what unless you see it fully loaded while in use.

 

[sw_ross]

Adjust it. That may be all it takes but something changed. You won’t know what unless you see it fully loaded while in use.

Would you lower it or increase it? Would it be set too high for the existing load and need to be dropped down 10-20%, or the opposite?

 

[synchro]

Given your fault code of "Regenerative Overvoltage Trip During Constant Speed" it might be more appropriate to utilize the Regeneration avoidance function described on pages 340-342 (306-308 in pdf) of the document linked below. This function momentarily increases the output frequency to prevent excessive DC bus voltage from regeneration. The stall prevention function instead momentarily decreases the frequency to avoid excessive current draw.

https://dl.mitsubishielectric.com/dl/fa/document/manual/inv/sh060014/sh060014engb.pdf

Now it may be possible that if the stall prevention function is too aggressive in limiting the output current then it might lower the frequency too much and/or too quickly and then cause an overvoltage. This might be why, as you mentioned, in a troubleshooting section they recommend that parameter 22 (stall prevention operation level) not be too small, because this would make the VFD try to keep the output current too low. However, if your setting is now at 150% out of a 200% maximum then that is less likely.

The Regeneration avoidance function has parameter 882 that when set to 2 makes it valid only for constant speed operation (the condition indicated in your error code).
If you activate this function, perhaps you could start by setting the voltage gain parameter 886 lower than the default 100% as suggested for higher inertia loads (maybe about 50%), and then increase it if you still get overvoltage trips with the gazebo loaded .

 

[RumRunner]

@OP

While I take everything you’ve said is the actual event/events that’s happening or have happened—I would not arbitrarily change the setting at this point (although-- perhaps that’s what it will take to correct it.)

You’ve indicated that the unit is: “the motor stalling out during usage.”

What I’m not quite clear is: what did they do to resume the operation? Did it restart when they pushed the start button? And what did you find when you showed up?
Now, let’s take that “stalling during usage” bit.
This tells me that the unit is experiencing unstable drag while in motion—not during accel or decel.
I’m sure you’ve done those T-shooting-- along with some suggestions by contributors --as to what might be happening. (the purpose of this forum)

I understand that you noted the cause of the anomaly.--and yet still need to be addressed.

This Mitsubishi Series 700 Model has a lot of improvements to it from their early models.
Before the unit trips on overload /over voltage, it goes thru a stage in which “it” enters a threshold where it determines whether a glitch is occurring (harmonics can cause this anomaly)
If the anomaly is sustained--depending on the duration—the overload protection would trip to protect the drive (VFD) and the motor.

This unit is capable of storing valuable information for convenient T-shooting.

Peruse the manual from cover to cover and it will tell you the history of the events that caused them-- or when the problem occurred.
It can store up to eight (8) events.

Keep us posted what you come up with.

Note:
As I was poring thru the manual—I noticed that this model is designed for a 1.5 HP motor minimum.
Your application (you said) is 1 HP.